Which Chlorine To Use For An Above Ground Pool

It is exciting to finally have a pool installed in your backyard and enjoy the ever-hot summer swimming. And having an above-ground pool is an easy-go way of owning a swimming pool on a budget and in the comfort of your home.

However, that doesn’t exclude it from the regular like adding chlorine. You probably already know there are several types of chlorine. So which one should you use for your pool? Can the wrong chlorine damage an above-ground pool?

For everyday chlorination of an above-ground pool, liquid chlorine (sodium hypochlorite aka bleach) or dichlor is are good choices. Use unstabilized chlorine if you have an outdoor pool with high stabilizer levels. Use stabilized chlorine if you have low stabilizer levels or an indoor pool.

Let’s take a closer look at what makes a good choice of chlorine for above-ground pools.

Above ground pool on grass in front of house.
Above-ground pool

Considerations Choosing Chlorine for an Above-Ground Pool

When choosing chlorine for an above-ground pool, it is important to first consider several factors that influence the kind of chlorine to use. Some of these factors include:

Size of the Pool

Larger pools may be more suitable for granular chlorine, while smaller pools, like most above-ground pools, can accommodate various forms of chlorine, such as liquid chlorine and solid tablets.

The Type of Pool

Pools can be categorized as saltwater or chlorine pools. Chlorine treatments like cal-hypo are not a good option if you have a saltwater pool. More about these are discussed in the article below. 

The Type of Above-Ground Pool

This refers to the kind of material surrounding or enclosing the pool. For example, resin pools, hybrid pools, aluminum pools, and steel pools. Trichlor chlorine shouldn’t come in direct contact with vinyl liner or fiberglass pool walls/floor.

Types of Chlorine Commonly Used In Above-Ground Pools

There are several types of chlorines available for above-ground swimming pools. The chlorine you use will depend on your pool’s chemistry, your pool equipment, and personal preference.

These include:

  • Chlorine tablets (come as trichlor, cal-hypo and sometimes dichlor)
  • Household bleach
  • Liquid chlorine (Sodium hypochlorite)
  • Granular or powdered chlorine (comes as trichlor, cal-hypo and dichlor)

Let’s take a close look at the chlorines for above-ground pools.

Liquid Chlorine (Sodium Hypochlorite)

Liquid chlorine, also known as bleach, is by far the most popular and widely used sanitizer. It is cheap, easy to use, and has the least amount of side effects or byproducts when poured into the pool water.

It has no cyanuric acid (CYA or stabilizer) but contains sodium hypochlorite that adds a little salt to your pool. It contains about 12.5% chlorine content and is readily available in local stores.

Liquid chlorine is a great choice for above-ground pools since it is not strong and mixes quickly with pool water.

Liquid Chlorine Pool Shock - Commercial Grade 12.5% Concentrated Strength - 1 Gallon

Can I Use Bleach in an Above-Ground Pool?

You may be wondering if it’s okay to add normal bleach such as Clorox, (thinking it’s liquid chlorine) into your pool. It’s perfectly fine to use bleach in your pool as long as it has no additives or scents.

It has no side effects and is extremely cheap. But you should know that bleach will only provide half the chlorine strength that liquid chlorine from a local pool store or supplier will provide. So you’ll need twice as much.

Clorox Performance Bleach, 121 oz, 3 ct

As a side note, the chlorine percentage you see displayed on the package is the strength chlorine will have in your pool. For example, you’ll see 12.5% chlorine or sodium hypochlorite listed on the bottle. This is the amount of chlorine available. Other chlorines are much stronger.

Pros

  • It acts fast – breaks down or sanitizes your pool quickly.
  • It’s highly convenient – you can pick up a jug of it at the grocery store and pour it into the pool whenever needed.
  • It does not increase CYA (stabilizer or cyanuric acid) levels in the pool. This is a great option for pools having high levels of cyanuric acid.
  • It is inexpensive, thus a great option if on a tight budget.
  • It is safe for use in all types of pools.

Cons

  • It has a short shelf-life. You’ll need to frequently restock.
  • It’s easily broken down by sunlight and thus your pool needs a CYA of 30 to 50 ppm to at least keep it steady.

Calcium Hypochlorite (Cal-Hypo)

This is also popular chlorine for above-ground pools. It is unstabilized and comes both in powder and tablet form with varied strengths of active chlorine ranging from 60 to 75%. 

However, it is not suitable for use in saltwater pools as cal-hypo leaves behind calcium. Also, if your water supply is hard or high in calcium, this isn’t a good option as it will further increase the calcium hardness.

In general, it’s best not to use cal-hypo for daily chlorination of above-ground pools. However, you can use it as a pool shock.

In The Swim Calcium Hypochlorite Chlorine Granular Pool Shock - 50 Pounds

Calcium in the water can build up which will cause other issues with your pool equipment and water balance. Instead, stick to using it as a pool shock.

Pros

  • Doesn’t raise CYA levels.
  • Has a much longer shelf-life compared to liquid chlorine (2 to 3 years).
  • It’s easy to use and is very strong.
  • It’s safe for all pool surfaces but shouldn’t directly contact pool surfaces.

Cons

  • Adds calcium deposits to the water and can leave stains on the walls and floor of your pool if applied directly.
  • Doesn’t have stabilizers.

Dichloro-S-Triazinetrione (Dichlor)

Also known as sodium dichloroisocyanurate, Dichloro-S-Triazinetrione is a form of granular-powdered chlorine that’s designed to quickly dissolve in water.

It has about 55% available free chlorine and is a stabilized type of chlorine with already 60 to 65% CYA in it.

Dichlor can be used in above-ground pools but should be used with caution.

It can be added directly to the pool and is available in a stabilized form for owners with pools exposed to sunlight. Since it contains a stabilizer, it’s essential to keep cyanuric acid levels between 30 to 60 ppm in saltwater pools and 30 to 50 ppm in chlorine pools.

Rx Clear Stabilized Granular Chlorine | One 50-Pound Bucket | Use As Bactericide, Algaecide, and Disinfectant in Swimming Pools and Spas | Fast Dissolving and UV Protected

Moreover, for every 10 ppm of chlorine added to your pool, the amount of cyanuric acid goes up by 9 ppm. Therefore, you need to be careful not to add too much dichlor or cyanuric acid will reduce the effectiveness of chlorine in the water.

Due to this side effect, most people prefer liquid chlorine or trichlor over dichlor for weekly pool maintenance and shocking.

Pros

  • It quickly dissolves in water.
  • It has a neutral pH.
  • It comes in pre-measured tablets or granules and is readily available.
  • It’s safe for a variety of pool surfaces including vinyl, plaster, resin, steel, and aluminum.
  • It has a long shelf-life.

Cons

  • It’s a little more expensive than other types of chlorine.
  • It can raise your pool’s CYA levels.

Trichloro-S-Triazetrione

Also known as Trichlor, this type of chlorine is usually available in tablet form (3” tablets), fine powder, and granular form. The granular and tablet forms make it popular among pool users and professionals as they are easily measurable.

The tablet form of trichlor is suitable for above-ground pools. It dissolves slowly in water and can be convenient for ongoing chlorination. It contains a higher percentage of available chlorine over dichlor.

CLOROX Pool&Spa XtraBlue 3-Inch Long Lasting Chlorinating Tablets, 5-Pound Chlorine

The granular chlorine should be carefully stored in a cool and dry area, to prevent it from overheating or absorbing moisture.

Like dichlor, it comes stabilized, and contains for every 10 ppm of chlorine, will add about 6 ppm of stabilizer. That’s a lot. You’ll have to cautiously add trichlor to your pool so you don’t increase your pool’s CYA levels too much. 

Trichlor releases free chlorine into the pool water slowly over time, providing a steady supply that can last for up to a week. As a result, it’s frequently used both as a sanitizer and to add a stabilizer.

Overuse of trichlor can lead to high cyanuric acid levels.

You need to be careful not to overuse trichlor. Overtime cyanuric acid levels will increase, since trichlor contains stabilizer. From time to time, switch to a non-stabilized chlorine. Trichlor is very powerful and you can easily add too much stabilizer.

Trichlor tablets normally contain 90% to 99% active chlorine and have low pH levels between 2-3. It’s more powerful than dichlor. If it comes in contact with above-ground pools with a vinyl liner or fiberglass walls, it can cause damage.

To reduce the chances of this happening, use a floating device or feeder. These devices aid in distributing trichlor in the pool evenly. Just be sure the floater doesn’t get stuck in one spot in the pool. This will cause a high concentration of chlorine in the area.

Pros:

  • It is convenient as it comes in pre-measured tablets.
  • It has a high chlorine content.
  • It contains cyanuric acid (stabilizer).
  • The slow release of chlorine is ideal for above-ground pools as it keeps the pool sanitized for longer periods.

Cons:

  • It is expensive.
  • It lowers pH levels in a pool.
  • It adds cyanuric acid to the pool which can raise CYA too high.

How to Determine What Chlorine to Use for My Above-Ground Pool?

To accurately determine the type of chlorine your pool needs, you’ll need to test and determine parameters like the pH, alkalinity, chlorine level, and TDS.

You can use a DPD Liquid Test Kit to determine the pool’s levels. 

Use the Taylor Test Kit for chlorine pools:

TAYLOR TECHNOLOGIES INC K-2006 TEST KIT COMP CHLORINE FAS-DPD

Use the Taylor Saltwater Test Kit for saltwater pools:

Taylor Technologies K-2006-SALT Test Kit

For example, if your pool has low cyanuric acid content, then dichlor or trichlor is a good option. As for pools with high cyanuric acid, it’s advisable to use liquid chlorine.

Is it OK to Switch or Use Chlorine Types?

You can have multiple chlorine types in your pool at the same time. But, do not mix them together when adding them, make sure you wait several hours between applications. More on that here: Can You Mix or Switch Chlorine Types? (Answered!)

How Can I Add Chlorine to My Above-Ground Pool?

Once you’ve determined your pool’s chemistry, the following are methods you can adopt when placing chlorine in your above ground pool:

  • Using a floating chlorine dispenser for tablets or pucks.
  • Automatic chlorinator (chlorine feeder) for tablets or pucks.
  • Dissolve in a bucket of water (cal-hypo, dichlor).
  • Pour directly into the pool (liquid chlorine aka sodium hypochlorite and bleach).

Is Stabilized or Unstabilized Chlorine Better for Above-Ground Pools?

Both stabilized and unstabilized chlorine should be used in outdoor above-ground pools.

Stabilized chlorine is great if your above-ground pool is outside in the backyard. The stabilizer (cyanuric acid) prevents free chlorine from dissipating into the atmosphere due to sunlight.

However, keep an eye on the stabilizer levels. They should be kept between 30-50 ppm for a chlorine pool and 30-60 ppm for a saltwater pool. If the stabilizer (CYA) levels are close to the upper limits, switch to unstabilized chlorine until the stabilizer levels reduce.

If you have an indoor pool, you can use unstabilized pool chlorine.

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